This invention relates generally to the field of processing foodstuffs particularly fruits, vegetables and cereal grains. More specifically, it relates to processing of such foodstuffs by procedures which include treatment with dilute aqueous solutions of hydrolysis mixtures of aldonic acids and their lactones or precursors thereof, especially gluconic acid, combined with a sulfite to control its appearance by preventing discoloration and/or reversing it by inhibiting enzymatic and/or oxidative discoloration. The acids as will be explained more fully hereinafter normally exist as a mixture of acids and lactones.
From the moment of harvest, food undergoes progressive deterioration and preventive measures are often taken to prolong storage life. Food preservation techniques should retain the nutritional value and prolong the stability of the foods' organoleptic properties. By this is meant those properties or qualities of the foodstuff determinable by use of one or more of the human sense organs. The organoleptic qualities include texture, color, flavor and/or aroma.
One of the most common manifestations of deterioration occurs in certain foodstuffs that are prone to enzymatic and/or oxidative discoloration, such as potatoes. It begins when the cell walls are disrupted when the foodstuff is peeled or its skin is cut, thus exposing them to air without the natural protection of the skin. This initial discoloration is probably exclusively enzymatic in nature. Oxidative discoloration continues after the enzymes have been deactivated by blanching, frying or cooking. With potatoes, the latter type of discoloration appears to be associated principally with oxidation of a ferrous ion complex with o-dihydoxphenols to form a colored complex with the ferric ion.
Numerous agents have been employed in attempts to maintain the natural color of foodstuffs by preventing, retarding, controlling, reversing or otherwise inhibiting the development or retention of discoloration. These have included various acids such as ascorbic, acetic (sometimes in the form of vinegar), citric (sometimes in the form of lemon juice) and malic. However, such acids often impart an acid or sharp flavor to foods with which they are employed. This detracts from the natural flavor of the food. Sodium pyrophosphate is also employed with potatoes for this purpose, but it has an adverse influence on texture, resulting in a mealier product.
Sulfiting agents have been used for hundreds of years in the processing of foods, especially to retard or reverse discoloration. Sulfiting agents which heretofore have been generally regarded as safe include sulfur dioxide, sodium and potassium bisulfite, sodium and potassium metabisulfite and sodium sulfite. Despite the widespread use of sulfiting agents, it has long been recognized that at the concentrations normally employed they impart undesirable flavors and odors which adversely affect the acceptance of foods with which they are used. Recently they have been implicated as initiators of asthmatic attack and other adverse reactions in hyperallergenic individuals. Additionally, the sodium containing agents add to the burden of hypertensive individuals. The Food and Drug Administration of the United States Government has recently imposed strict controls on sulfiting agents for use in connection with potatoes, and other foodstuffs, and a requirement for label declaration of residues of 10 ppm or more for foodstuffs intended to be served or sold to the public.
The limitations or outright banning of sulfiting agents will have a direct impact on food service establishments especially restaurants, supermarkets and salad bars. It is the practice in such food distribution centers to spray the produce with aqueous sulfite solutions to maintain an attractive appearance of freshness by retarding or reversing discoloration. It will also be a problem for food processors and packagers who have long utilized sulfiting agents to inhibit deterioration, especially discoloration of raw foodstuffs or foods such as potatoes, which have been dehydrated, frozen, par-fried, fried, cooked or otherwise processed.
Sulfiting agents have been employed in a wide range of food products which are subject to discoloration including dried fruits, lettuce, potatoes, cauliflower, maraschino cherries, sauerkraut, pickled peppers, corn starch, hominy, fresh mushrooms, soup mixes, crabmeat, pizza and pie dough, fruit salad, grapes and other fruits, vegetables and cereal grains.